three days ago i wok up with a little bump on the side of my knee that looked like a mosquito bite. but later it started to hurt and it got a big dark red circle around it. the bump is still in the middle, its white and still really small. my leg is swollen right there and is warm if you touch it.... any ideas what it is? or what i should do with it?

oh yah and i have volleyball tomorrow so i have to wear knee pads.... good idea or not?